1. Field
One or more example embodiments relate to an optical signal transmission system and method that may transmit and receive optical signals by allocating center frequencies of intermediate frequency (IF) carriers in a frequency division multiplexing (FDM) optical fiber link.
2. Description of Related Art
One or more example embodiments relate to a method of allocating center frequencies of intermediate frequency (IF) carriers to prevent distortion in view of secondary distortion components generated by chirps and chromatic dispersion of lasers in an optical link using frequency division multiplexing (FDM) transmission.
The optical link using FDM transmission employs direct amplitude modulation that converts current amplitudes of modulated signals into a power amplitude of an optical signal. In this example, due to a chirp phenomenon of a laser, an oscillation frequency may change based on an put current. In detail, the change caused by the chirp phenomenon may not have effect in a wavelength in which optical fiber chromatic dispersion is absent. However, in a wavelength in which optical fiber chromatic dispersion is present, chirps and the dispersion may be combined and signal distortion components may appear.
U.S. Pat. No. 5,608,562 discloses a structure using a dispersion compensation fiber (DCF) to eliminate effects by fiber chromatic dispersion. However, in the structure of U.S. Pat. No. 5,608,562, an optical fiber of a length corresponding to a cumulative amount of dispersion of an optical fiber line needs to be inserted, and thus a feedback structure is required and a cost for implementation may increase.
Further, U.S. Pat. No. 7,945,172 discloses a dispersion compensation device of a feedforward structure using a predistortion circuit. However, in the structure of U.S. Pat. No. 7,945,172, an amplitude or phase of a separate dispersion compensation path, or a delay with respect to the original signal needs to be controlled precisely, and thus a size of the device and a cost may increase.
Accordingly, an optical signal transmission method that may prevent signal distortion without using a dispersion compensation optical fiber or performing complex signal processing is provided herein.